Messier 97, 108 & NGC 3631 — Wide Field
Key Scientific Data
Main objects: M97 (Owl Nebula), M108 (Surfboard Galaxy), NGC 3631
Constellation: Ursa Major
Object types: M97 – planetary nebula; M108 – nearly edge-on spiral galaxy; NGC 3631 – face-on spiral galaxy
Other designations: M97 (NGC 3587), M108 (NGC 3556), NGC 3631 (PGC 34767)
M97 distance: approximately 2,000 light-years
M108 distance: approximately 45–50 million light-years
NGC 3631 distance: approximately 50 million light-years
M97 apparent magnitude: approximately 9.9
M108 apparent magnitude: approximately 10.0
NGC 3631 apparent magnitude: approximately 10.4
Light-travel time: approximately 2,000 to 50 million years, depending on the object
Description
This wide-field image of Ursa Major brings together three distinct astronomical objects: the planetary nebula Messier 97, the nearly edge-on spiral galaxy Messier 108, and the face-on spiral galaxy NGC 3631.
Although they appear close together in the sky, they are separated by enormous distances. M97 belongs to our Milky Way, while the two galaxies lie approximately 50 million light-years away.
The photograph therefore combines the final evolutionary stage of an individual star with two entire galaxies, offering a striking illustration of the Universe's immense depth.
M97 – The Owl Nebula
Messier 97, commonly known as the Owl Nebula, is a planetary nebula approximately 2,000 light-years from Earth.
It formed when a dying star expelled its outer atmosphere, leaving behind a hot stellar remnant whose ultraviolet radiation ionises the surrounding gas.
Its characteristic appearance comes from two darker regions within the roughly circular nebula, resembling the eyes of an owl. The central star is evolving towards the white-dwarf stage.
M108 – The Surfboard Galaxy
Messier 108 is a spiral galaxy viewed almost edge-on, giving it the elongated appearance responsible for its nickname, the Surfboard Galaxy.
Located approximately 45–50 million light-years away, it contains prominent dust lanes and numerous star-forming regions distributed across its disc.
Its highly inclined orientation largely conceals the spiral pattern, revealing instead the complex distribution of stars, gas and dust along the galactic plane.
NGC 3631 – A Face-on Spiral
NGC 3631 is a spiral galaxy located approximately 50 million light-years from Earth.
Unlike M108, its nearly face-on orientation reveals a well-defined spiral structure, with prominent arms extending around a bright central region.
These arms contain concentrations of young stars and ionised hydrogen, indicating ongoing star formation.
The contrasting orientations of M108 and NGC 3631 provide two complementary perspectives on the structure of spiral galaxies.
A Field Full of Galaxies
Beyond the three principal objects, the image reveals numerous faint background galaxies, many identifiable by their PGC catalogue designations.
Some appear as tiny elongated structures or faint patches of light between foreground stars belonging to the Milky Way.
This exceptionally rich extragalactic field explains the choice of broadband RGB imaging, which preserves the continuum light and natural colours of galaxies and stars.
Although narrowband Hα and OIII filters would reveal more detail within M97, they would suppress much of the light from the surrounding galaxies, making broadband imaging better suited to this composition.
Looking Back in Time
This photograph captures light originating from dramatically different periods of cosmic history.
The photons from M97 began their journey approximately 2,000 years ago, around the beginning of the Roman Imperial period.
By contrast, the light from M108 and NGC 3631 has travelled for approximately 45–50 million years, originating during Earth's Eocene epoch.
At that time, Earth was considerably warmer, mammals were diversifying, and early ancestors of modern horses, whales and primates were evolving. Humans had not yet appeared.
Within a single photograph, we are therefore observing objects as they existed thousands and tens of millions of years ago, illustrating the extraordinary range of distances and epochs contained in a small region of the night sky.
Image Data
Total integration time: 4h 06m
Integration by filter:
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Red: 1h 54m (38 × 180")
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Green: 1h 12m (24 × 180")
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Blue: 1h (20 × 180")
Equipment:
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Telescope: William Optics RedCat / Cat 51 III WIFD
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Camera: ToupTek ATR2600M
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Mount: 10Micron GM2000 HPS II
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Filters: Optolong Blue 2", Optolong Green 2", Optolong Red 2"
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Accessories: ToupTek AAF Electric Focuser, WandererAstro WandererCover V4-EC
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Software: Adobe Photoshop, Pleiades Astrophoto PixInsight, Stefan Berg Nighttime Imaging 'N' Astronomy (N.I.N.A. / NINA)
For further details and the full-resolution image, visit AstroBin: